Conventionally, in construction machines, factory equipment, etc. for forming a flow path (e.g., oil path) for transporting a fluid at high temperature and high pressure (e.g., oil), a hose composed of a rubber layer with an inner circumferential side in contact with the fluid is used. This hose has at least a metallic wire layer and an inner tube rubber layer arranged on a circumferential side inner than this metallic wire layer. Examples include one constituted by respectively laminating the inner tube rubber layer, the metallic wire layer, an intermediate rubber layer and an outer coating rubber layer from a radial inner side to an outer side. Moreover, this hose is, for example, connected to a machine, device, etc. into which a fluid is transported, via a metallic mouthpiece attached to both ends of the hose.
During long-term use of the aforementioned hose, in particular, gradual thermal aging due to heat from the fluid, etc. of the rubber layer on the inner circumferential side is unavoidable, and if the rubber layer suffers from excessive thermal aging, there would be a defect due to degradation of the rubber layer, such as that the fluid inside the hose leaks from the mouthpiece. In order to avoid occurrence of such defect, it is effective to previously avoid using a hose including an excessively degraded rubber layer, by regularly diagnosing a degrading situation of the hose, or predicting a remaining life until a use limit of the hose.
In view of such situation, we discovered that it is effective to measure a reaction force of the hose in order to diagnose the degrading situation of the hose.
Examples of a device for measuring the reaction force of the hose include a bending reaction force measuring device, which, when an elongated test hose with both ends fixed is bent into a semicircular shape between two points, measures the bending reaction force generated between the two points by using a detector disposed at either one of the two points (see JPH10-288575A (PTL1)).